Irregular outlines appearing in pockets

Can someone please tell me what’s going on with the irregular lines appearing in the pockets of some of my signs. The flash accentuates the effect in this photo.

This sign was carved from .5" thick HDU on my XL with a .25" end mill.


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Hello, very nice, your sign I think that the marks of the cutter are caused by lack of adjustment, I mean the perpenticularity and parallelism. It must be adjusted very well to improve the finish of the tools.


Agree w/ @JoseD3 — to expand on that, MDF and coarser grained woods will compress when cutting and expand afterwards — best thing to do is make a finishing pass w/ a nice sharp endmill (HSS tends to be sharper than carbide).

Please see and the section on squaring the spindle below that.

Alternately, use a CAM tool to create a textured surface along the bottom.

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What they said.

Much of it appears to be from finish pass waterlining. An option, if you don’t want a textured finish, is to run a finish pass over the bottom surface as a last operation.


The machine has a Belt and this belt does have some deflection (caused by tool deflection). Always take a finish (with no extra Z depth material). This used to be a pain in the butt before, but now Carbide Create allows you to set the Z height for a 2nd pass.


Thanks to all who responded with suggestions for this perplexing problem. I discovered my spindle is not quite perpendicular even though the frame, waste board, side rails and gantry are all well within an acceptable tolerance. I did mic the mounting holes for the router mounting bracket on the Z Axis plate (to the edge of that plate) and noted that they do not match by about .005". Is that enough to create the effect you see in my photo?

The only thing I can think to do is enlarge the router mounting holes on the Z plate slightly, which would allow me to tweak the bracket in the right direction. Does this make sense or is there a better approach?

Last, a finishing pass intrigues me… I am new to CNC operations, do you have a link to this process?

Thanks again!!